Recently, there are suggested various electronic endoscopes wherein such solid state imaging device as a charge coupled device (CCD) is used as an imaging means.
Such electronic endoscope has advantages that it is higher in resolution than a fiber scope, that it is easier to record and reproduce picture images and that such picture image processes as the magnification of picture images and comparison of two pictures are easier.
Now, conventionally, there are side viewing type electronic endoscopes wherein, as shown in the gazette, for example, of a Japanese patent application laid open No. 47921/1986, an illuminating window and observing window are provided on the side surface of the tip part of the insertable part and a solid state imaging device is arranged to interest substantially at right angles with the axial direction of the insertable part on the base side more than this illuminating window and observing window or a solid state imaging device is arranged to interest substantially at right angles with the axial direction of the insertable part on the tip side more than the above mentioned illuminating window and observing window.
This side viewing type electronic endoscope having a forceps channel is divided into two parts in a plane including the axial center line of the tip part, a forceps raising stand, forceps channel and raising wire are provided on one side half and therefore it is unavoidable that the other contents concentrate on the other half. Therefore, in order to make the diameter small, it is important to arrange the above mentioned contents at a high space efficiency.
In the solid state imaging device arranged on the base side, the illuminating window is provided on the tip side more than the observing window and the light guide of fibers is passed through the side (the side reverse to the observing window) below the solid state imaging device to make the diameter small.
Also, in the solid state imaging device arranged on the tip side, the observing window is provided on the tip side more than the illuminating window and the cable connected to the solid state imaging device is returned to the lower side (the side reverse to the observing window) of the solid state imaging device and is inserted to make the diameter small.
The electronic endoscope requires not only a solid state imaging device but also peripheral circuits for amplifying video output signals from the solid state imaging device and for forming solid state imaging device driving pulses. Signal cables electrically connecting solid state imaging apparatus including these peripheral circuits with a camera control unit for processing signals are required to be about 12 in the case of the most general four-phase driving type CCD. It is preferable to use shielding wires for these signal cables to prevent noises. Therefore, the diameter of one signal cable will become large and a considerable space will be required for wiring signal cables.
On the other hand, about 14 bonding wires for electrically connecting a solid state imaging device chip with a solid state imaging device package base are required for a four-phase driving type CCD. The space for the wire bonding is required to be about 3 mm.times.1 mm from the pitch of the above mentioned bonding wires and the space for providing bonding pads. This size is required to make the diameter small. This size is an innegligible size as of an endoscope in which the diameter is required to be small and, for example, the outside diameter of the insertable part is about 10 mm for the upper or lower digestive organ.
However, where the wire bonding part occupying such large space is to be provided to make the diameter smallest has not been considered. Therefore, the diameter of the insertable part has not yet been made small enough in the arrangement of the solid state imaging device either on the base side or on the tip side.